"The Physicians' Health Study II is the first clinical trial to test the affects of multivitamins on a major disease such as cancer," said lead author J. Michael Gaziano, MD, chief of the Division of Aging at BWH and an investigator at VA Boston. "Despite the fact that more than one-third of Americans take multivitamins, their long-term effects were unknown until now."

Researchers had nearly 15,000 men over the age of 50 take either a multivitamin or a placebo every day for more than 10 years. (From the monthly multivitamin packs pictured here.) The men self-reported a cancer diagnosis, and researchers confirmed the diagnosis through medical records. Researchers found the group taking a daily multivitamin had an 8 percent reduction in total cancer compared with the group taking the placebo. They also found a multivitamin was associated with an apparent reduction in cancer deaths.

Study co-author Howard D. Sesso, ScD, an associate epidemiologist in the Division of Preventive Medicine at BWH said, "Many studies have suggested that eating a nutritious diet may reduce a man's risk of developing cancer. Now we know that taking a daily multivitamin, in addition to addressing vitamin and mineral deficiencies, may also be considered in the prevention of cancer in middle-aged and older men."

Researchers point out that it is not clear which specific vitamins or minerals in a multivitamin may be responsible for the reduction in cancer risk. Also, it is not known if the results can extend to women or to men younger than the age of 50. Researchers plan to follow up with study participants to determine the affect of a daily multivitamin on cancer over an even longer period of time.

A similar study is examining the affect of daily multivitamin use on cardiovascular disease risk. Results of that study will be announced at the American Heart Association Scientific Sessions in early November.

This research was supported by grants CA 097193, CA 34944, CA 40360, HL 26490, and HL 34595 from the National Institutes of Health, and an investigator-initiated grant from BASF Corporation. Study agents and packaging were provided by BASF Corporation and Pfizer (formerly Wyeth, American Home Products, and Lederle). Study packaging was provided by DSM Nutritional Products, Inc. (formerly Roche Vitamins).